The present invention is directed to filter media having microbiological interception capability, filtration systems containing such filter media, and methods of making and using same.
Modern consumer water filters often provide xe2x80x9chealth claimsxe2x80x9d including reduction of particulates, heavy metals, toxic organic chemicals, and select microbiological threats. These filtration systems have been able to intercept microorganisms such as Cryptosporidium and Giardia using roughly 1.0 micron structures. However, in order to provide microbiological interception of even smaller microbiological threats such as viruses, a filter medium having a sub-micron microporous structure is required. Prior art filtration systems often attempt to achieve broad microbiological interception using filter media with insufficiently small pore size and with poor physical integrity. The balance between the necessary pore structure required for successful microbiological interception and satisfactory filter performance has not been achieved. In addition, prior art systems did not provide devices capable of operating in the presence of xe2x80x9cinterferencesxe2x80x9d consisting of substances that cause a loss of filtration performance.
The present invention is directed to, in a first aspect, a filter medium comprising: a microporous structure having a mean flow path of less than or equal to about 1 micron; and a microbiological interception enhancing agent comprising a cationic metal complex capable of imparting a positive charge on at least a portion of the microporous structure.
In another aspect, the present invention is directed to a composite filter medium comprising: an adsorbent prefilter having immobilized therein a material capable of removing charge-reducing contaminants; a microporous structure, disposed downstream from the adsorbent layer, comprising a plurality of nanofibers, the microporous structure having a mean flow path of less than about 0.6 micron; and a microbiological interception enhancing agent comprising a silver-cationic material-halide complex having a high charge density, coated on at least a portion of a surface of at least some of the plurality of fibers of the microporous structure.
In yet another aspect, the present invention is directed to a filter system comprising: a granular bed of particles capable of removing charge-reducing contaminants; a microporous structure, disposed downstream from the granular bed, having a mean flow path of less than about 0.6 micron; and a microbiological interception enhancing agent comprising a silver-cationic material-halide complex having a high charge density, coated on at least a portion of a surface of the microporous structure.
In still yet another aspect, the present invention is directed to a filter system comprising: a solid composite block comprising a material capable of removing charge-reducing contaminants; a microporous structure, disposed downstream from the block, having a mean flow path of less than about 2.0 microns; and a microbiological interception enhancing agent comprising a silver-cationic material-halide complex having a high charge density, coated on at least a portion of a surface of the microporous structure.
In still yet another aspect, the present invention is directed to a process of making a filter medium comprising the steps of: providing a microporous structure having a mean flow path of less than about 1 micron; and coating at least a portion of the microporous structure with a microbiological interception enhancing agent, the microbiological interception enhancing agent comprising a cationic metal complex capable of imparting a positive charge on at least a portion of the microporous structure.
In a further aspect, the present invention is directed to a process for making a filter medium comprising the steps of: providing a plurality of nanofibers; coating at least a portion of a surface of at least some of the plurality of nanofibers with a microbiological interception enhancing agent, the microbiological intercepting agent comprising a cationic metal complex; and forming the fibers into a microporous structure having a mean flow path of less than about 1 micron.
In still a further aspect, the present invention is directed to a process for making a filter medium comprising the steps of: providing a plurality of polymer nanofibers; coating at least a portion of a surface of at least some of the plurality of polymer nanofibers with a microbiological interception enhancing agent, the microbiological intercepting agent comprising a cationic metal complex; and forming a microporous structure having a mean flow path of less than about 1 micron.
In still a further aspect, the present invention is directed to a process for making a filter medium comprising the steps of: providing a plurality of cellulose nanofibers; coating at least a portion of a surface of at least some of the plurality of cellulose fibers with a microbiological interception enhancing agent, the microbiological intercepting agent comprising a cationic metal complex; and forming a microporous structure having a mean flow path of less than about 1 micron.
In still yet a further aspect, the present invention is directed to a process of making a filter medium comprising the steps of: providing a membrane having a mean flow path of less than about 1 micron; and coating at least a portion of the membrane with a microbiological interception enhancing agent, the microbiological interception enhancing agent comprising a cationic metal complex capable of imparting a positive charge on at least a portion of the membrane.
In still yet a further aspect, the present invention is directed to a process for making a filter medium comprising the steps of: providing a plurality of nanofibers; coating at least a portion of a surface of at least some of the plurality of the nanofibers with a microbiological interception enhancing agent, the microbiological intercepting agent comprising a silver-amine-halide complex having a medium to high charge density and a molecular weight greater than 5000 Daltons; and forming a microporous structure having a mean flow path of less than or about 0.6 microns.
In still yet a further aspect, the present invention is directed to a process for making a filter system comprising the steps of: providing an adsorbent prefilter comprising a material capable of removing charge-reducing contaminants from an influent, wherein the material is immobilized into a solid composite block; providing a plurality of nanofibers; coating at least a portion of a surface of at least some of the plurality of the nanofibers with a microbiological interception enhancing agent, the microbiological intercepting agent comprising a silver-amine-halide complex having a medium to high charge density and a molecular weight greater than 5000 Daltons; and forming a microporous structure having a mean flow path of less than or about 0.6 microns.
In still yet a further aspect, the present invention is directed to a method of removing microbiological contaminants in a fluid comprising the steps of: providing a filter medium having a microporous structure having a mean flow path of less than about 1 micron, the microporous structure having coated on at least a portion thereof a microbiological interception enhancing agent comprising a cationic metal complex wherein the cationic material has a medium to high charge density and a molecular weight greater than about 5000 Daltons; contacting the fluid to the filter medium for greater than about 3 seconds; and obtaining at least about 6 log reduction of microbiological contaminants smaller than the mean flow path of the filter medium, that pass through the filter medium.
In still yet a further aspect, the present invention is directed to a gravity-flow filtration system for treating, storing, and dispensing fluids comprising: a first reservoir for holding a fluid to be filtered; a filter medium in fluid communication with the first reservoir, the filter medium comprising a microporous structure with a mean flow path of less than about 1 micron, and wherein the filter medium is so treated as to provide at least about 4 log reduction of microbiological contaminants smaller than the mean flow path of the filter medium; and a second reservoir in fluid communication with the filter medium for collecting a filtered fluid.